36 



NATURE SKETCHES IN TEMPERATE AMERICA 



have the nectar sliallowly held in the hollow sepals accessible 

 to a great \'ariety of insect guests. 1'he scent of these flowers 

 is perceived for a distance of se\eral hundred yards; the parafBn- 

 oids composing it have the jjeculiar property of increasing in 

 intensity the farther away the perfume floats on the air up to 

 a certain distance, when it finally disperses by diffusion through 

 the air. In view of these facts, it is not difficult to ])erceive 

 why the iieclar gatherers have preference for the Itasswood 

 flowers. 



How THE ^Milkweed Profits by the 

 Visits of its Insect Guests 



N another cha])tcr on the Monarch Butter- 

 fly and its JVlimic, 1 will refer to the 

 familiar banded larva found on the milk- 

 weed. On this plant are also found cer- 

 tain oLher insects. One can hardly think 

 of the greenish purple umbels of the 

 common miUcwceJ without associating with these exquisitely 

 perfumed flowers the red, four-spotted beetle, Tetraopes tctra- 

 ophthabnus. This small beetle, which has blackish antcnufe, 

 is often seen in -July resting on the leaves, singly or in pairs, 

 as depicted in the colored plate (facing page 36). On sun- 

 shiny days it is also seen flying from one plant to another. 

 The life of this insect is intimately connected with the milkweed, 

 the roots and lower parts of the stems of this plant furnishing 

 nutrition for the larvae which penetrate and feed upon them. 



Besides the almost constant presence of (he red, four-spotted 

 beetle, the perfumed flowers entice winged insects of many 

 kinds. These include such forms as hees, wasps, flies, butter- 

 flies, moths, beetles, and occasionally bugs. Guided by the 

 scent, the insects are easily led to the honey. But while the 

 insects are in cpiest of this food, there is a reciprocal process 

 between plant and guest. At the same time they visit the 

 flowers they perform poUination, which is of great importance 

 to the plant's perpetuation. The dependence of these plants 

 upon insects as agents for transferring pollen is shown 

 by the peculiar structure of the flowers, many of them 



